Treatment method for tail gas of silane prepared by chlorosilane disproportionation method

Abstract

The invention provides a method for treating tail gas of preparing silane by a chlorosilane disproportionation method, which comprises the following steps: feeding the tail gas discharged by a silane safety valve into a first leaching system to obtain leached alkali liquor A; the leached alkali liquor A is fed into a recovery unit for recovery treatment, and recovered alkali liquor is obtained; the silane tail gas enters a second leaching system, and leached alkali liquor B is obtained; the method comprises the following steps: carrying out first condensation treatment on chlorosilane safety valve discharge tail gas to obtain first chlorosilane condensate and first condensed tail gas; carrying out second condensation treatment on the chlorosilane tail gas to obtain second chlorosilane condensate and second condensed tail gas; mixing the first condensed tail gas with the second condensed tail gas to obtain mixed chlorosilane tail gas; the mixed chlorosilane tail gas enters a third leaching system, and leached alkali liquor C is obtained; and returning the leached alkali liquor B and the leached alkali liquor C to the recovery unit, and carrying out recovery treatment together with the leached alkali liquor A. The technical scheme provided by the invention synchronously realizes innocent treatment of the tail gas of silane prepared by a plurality of chlorosilane disproportionation methods.

Description

Technical Field

[0001] The present invention relates to the field of silane preparation and tail gas treatment, and more particularly, to a method for treating tail gas from the disproportionation of chlorosilane to produce silane. Background Art

[0002] In the method of producing silane by the disproportionation of chlorosilane, the following types of tail gas are generated in the system: (1) Tail gas of chlorosilane: mainly the uncondensed chlorosilane tail gas discharged from the chlorosilane rectification tower and chlorosilane storage tank. These tail gases are common and the flow rate is relatively stable. The composition of this type of tail gas is complex. In addition to chlorosilane, there are also hydrogen, nitrogen, and hydrogen chloride gas. However, most of the chlorosilane can be recovered and reused after compression and condensation, thereby reducing the load on the tail gas scrubbing device. (2) Tail gas discharged from the chlorosilane safety valve: mainly the accident chlorosilane tail gas discharged from the safety valves of the chlorosilane rectification tower and chlorosilane storage tank. These tail gases are temporary, with a short duration but a large flow rate, and there is no flow rate when not discharging. This type of tail gas is mainly composed of chlorosilane. After cooling, most of the chlorosilane can be condensed and separated, and the remaining non-condensable gas needs to be scrubbed. Generally, after recovering chlorosilane, the chlorosilane safety valve discharge tail gas can be combined with the chlorosilane tail gas and treated together. (3) Tail gas of silane: mainly the silane tail gas discharged from the silane rectification tower and silane storage tank. These tail gases are common and the flow rate is relatively stable. This type of tail gas is mainly composed of silane gas, and there are also components with very low boiling points such as hydrogen and methane gas, which are difficult to be condensed again and can be directly scrubbed. (4) Tail gas discharged from the silane safety valve: mainly the accident chlorosilane tail gas discharged from the safety valves of the chlorosilane rectification tower and chlorosilane storage tank. These tail gases are temporary, with a large flow rate when the safety valve discharges, and there is no flow rate when not discharging. This type of tail gas is mainly composed of silane gas, which is difficult to be condensed again and can be directly scrubbed.

[0003] For the tail gas containing chlorosilane, water washing can be used. The generated hydrogen can be directly vented, hydrogen chloride dissolves in water to form hydrochloric acid, and silicon dioxide floats on the surface of the hydrochloric acid and forms harmless solid waste after treatment. The relevant reaction formula is as follows:

[0004] SiH n Cl 4-n +2*H2O→SiO2+(4-n)*HCl+n*H2 n=1,2,3,4

[0005] In addition, there is also prior art that uses an alkali solution to treat chlorosilane, and the reaction formula is as follows:

[0006] SiH n Cl 4-n +2*NaOH+H2O→Na2SiO3+4-n)*HCl+n*H2 n=1,2,3,4

[0007] However, for tail gas containing silane, since silane has a very low solubility in acidic water, but a high solubility in alkaline aqueous solution (usually NaOH), it can react violently with oxygen and cause combustion or explosion. Therefore, silane gas is usually treated by eluting with alkaline solution or burning. The relevant reaction formula is as follows:

[0008] SiH4+2*NaOH+H2O→Na2SiO3+4*H2

[0009] SiH4+2*O2→SiO2+2*H2O

[0010] The low pH (pH < ~9.5) aqueous sodium metasilicate solution produced during the above reaction, also known as water glass, is viscous and has poor fluidity, which can cause blockages in related system pipes. Furthermore, the water glass obtained through exhaust gas contains a large number of impurities, making it economically low, difficult to sell, and unsuitable for direct landfill disposal. Therefore, the treatment of silane-containing exhaust gas mainly relies on silane combustion. To prevent deflagration, the silane content is diluted to a low level. However, if a safety valve suddenly releases a large amount of silane exhaust gas, the silane content will seriously exceed the standard, compromising safety. Using a perpetual flare would be costly and require a high site.

[0011] In summary, the tail gas treatment of silane produced by the chlorosilane disproportionation method generally uses water to rinse the chlorosilane tail gas. For silane-containing tail gas, if the alkali washing method is also adopted, a batch production method of multiple towers in parallel and tower-by-tower elution is generally adopted, but it will produce a lot of waste alkali liquid that needs to be treated, and if the operation is improper, the solution will form water glass that blocks the equipment and pipelines. If different types of tail gas are treated separately, it is necessary to build multiple tail gas treatment and wastewater treatment systems, the comprehensive utilization efficiency of materials is not high, and the investment is huge. In addition, the methods currently used either mainly treat a single and small amount of silane tail gas, or the operating cost is huge and the site requirements are high, making it difficult to implement.

[0012] Based on this, how to provide a treatment method for the tail gas produced by the silane disproportionation method of chlorosilane to simultaneously achieve efficient treatment of the tail gas containing chlorosilane and the tail gas containing silane is one of the important technical problems that need to be solved in this field. Summary of the Invention

[0013] The main purpose of the present invention is to provide a method for treating tail gas produced by the chlorosilane disproportionation process to solve the problem in the prior art that it is difficult to simultaneously and efficiently perform harmless treatment on multiple tail gases produced in the chlorosilane disproportionation process to produce silane, namely, tail gas discharged from a silane safety valve, silane tail gas, tail gas discharged from a chlorosilane safety valve, and tail gas discharged from a chlorosilane tail gas.

[0014] To achieve the above object, the present invention provides a method for treating the tail gas of silane produced by the disproportionation of chlorosilane, comprising: Step S1, providing the tail gas of silane produced by the disproportionation of chlorosilane, which includes the tail gas discharged from the silane safety valve, the silane tail gas, the tail gas discharged from the chlorosilane safety valve, and the chlorosilane tail gas; Step S2, the tail gas discharged from the silane safety valve enters the first rinsing system, and after being first rinsed with an aqueous sodium hydroxide solution with a mass concentration of 10% to 25%, the rinsed alkaline solution A and the rinsed tail gas A are obtained; the rinsed alkaline solution A is sent to the recovery unit for recovery treatment to obtain the recovered alkaline solution; the silane tail gas enters the second rinsing system, and after being second rinsed with the recovered alkaline solution, the rinsed alkaline solution B and the rinsed tail gas B are obtained; Step S3, the tail gas discharged from the chlorosilane safety valve undergoes a first condensation treatment to obtain a first chlorosilane condensate and a first condensed tail gas; the chlorosilane tail gas undergoes a second condensation treatment to obtain a second chlorosilane condensate and a second condensed tail gas; the first condensed tail gas and the second condensed tail gas are mixed to obtain a mixed chlorosilane tail gas; the mixed chlorosilane tail gas enters the third rinsing system, and after being third rinsed with the recovered alkaline solution, the rinsed alkaline solution C and the rinsed tail gas C are obtained; Step S4, the rinsed alkaline solution B and the rinsed alkaline solution C are returned to the recovery unit and jointly undergo recovery treatment with the rinsed alkaline solution A; wherein, the recovery unit includes a precipitation reaction tank and a filter press connected in sequence, quicklime is added to the precipitation reaction tank for precipitation reaction to obtain a precipitation slurry, and the filter press is used to filter the precipitation slurry to obtain a solid precipitate and the recovered alkaline solution.

[0015] Further, the mass concentration of sodium hydroxide in the recovered alkaline solution is 2% to 5%.

[0016] Further, the first rinsing system includes two sets arranged in parallel, and each set of the first rinsing system includes a rinsing tower and an alkaline solution circulation pump arranged outside the rinsing tower, and the alkaline solution circulation pump is used to circulate the aqueous sodium hydroxide solution into the rinsing tower to complete the first rinsing.

[0017] Further, in the two sets of the first rinsing systems, one set is in a continuous operation state and the other set is in standby; at the same time, the spraying amount of the continuously operating set is less than that of the standby set, and the opening and closing state of the standby set changes with the intake pressure of the continuously operating set. When the intake pressure exceeds the threshold value, the standby set changes from the closed state to the open state.

[0018] Further, the threshold value is 0.075 MPa to 0.15 MPa.

[0019] Further, the threshold value is 0.1 ± 0.02 MPa.

[0020] Further, the precipitation reaction is carried out under normal temperature and pressure conditions.

[0021] Further, the temperature of the first condensation treatment and the second condensation treatment are each independently -10°C to -40°C.

[0022] Further, the temperatures of the first condensation treatment and the second condensation treatment are each independently -20 ± 2°C.

[0023] Furthermore, the recovered lye is divided into a first part, a second part, and a third part. The first part is used for the second rinsing, and the second part is used for the third rinsing. The method for treating the tail gas from the disproportionation of chlorosilane to produce silane further includes: Step S5, discharging the third part of the recovered lye into a neutralization reaction tank, adding hydrochloric acid to the neutralization reaction tank, and obtaining a sodium chloride solution after the neutralization reaction; the sodium chloride solution is subjected to evaporation crystallization to obtain sodium chloride crystals and condensed water, and the condensed water is returned to Step S4 for pressure filtration treatment.

[0024] Applying the technical solution of the present invention, a new method for treating the tail gas from the disproportionation of chlorosilane to produce silane is proposed. This method can synchronously treat different types of tail gases. By using sodium hydroxide solution rinsing and quicklime precipitation reaction, it effectively removes harmful substances in the tail gas discharged from the silane safety valve, silane tail gas, tail gas discharged from the chlorosilane safety valve, and chlorosilane tail gas, that is, synchronously realizes the harmless treatment of multiple tail gases. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The specification drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0026] Figure 1 It shows a schematic flow chart of the method for treating the tail gas from the disproportionation of chlorosilane to produce silane in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0028] As described in the background art, in the prior art, there is a problem that it is difficult to efficiently and harmlessly treat multiple tail gases generated during the disproportionation of chlorosilane to produce silane, namely, the tail gas discharged from the silane safety valve, silane tail gas, tail gas discharged from the chlorosilane safety valve, and chlorosilane tail gas, simultaneously. To solve the above technical problems, the present invention provides a method for treating the tail gas from the disproportionation of chlorosilane to produce silane, as Figure 1As shown in the figure, the treatment method includes: Step S1, providing the tail gas from the disproportionation of chlorosilane to produce silane, which includes the tail gas discharged from the silane safety valve, the silane tail gas, the tail gas discharged from the chlorosilane safety valve, and the chlorosilane tail gas; Step S2, the tail gas discharged from the silane safety valve enters the first rinsing system and is first rinsed with an aqueous sodium hydroxide solution with a mass concentration of 10% - 25% to obtain the rinsed alkaline solution A and the rinsed tail gas A; the rinsed alkaline solution A is sent to the recovery unit for recovery treatment to obtain the recovered alkaline solution; the silane tail gas enters the second rinsing system and is second rinsed with the recovered alkaline solution to obtain the rinsed alkaline solution B and the rinsed tail gas B; Step S3, the tail gas discharged from the chlorosilane safety valve undergoes a first condensation treatment to obtain the first chlorosilane condensate and the first condensed tail gas; the chlorosilane tail gas undergoes a second condensation treatment to obtain the second chlorosilane condensate and the second condensed tail gas; the first condensed tail gas and the second condensed tail gas are mixed to obtain the mixed chlorosilane tail gas; the mixed chlorosilane tail gas enters the third rinsing system and is third rinsed with the recovered alkaline solution to obtain the rinsed alkaline solution C and the rinsed tail gas C; Step S4, the rinsed alkaline solution B and the rinsed alkaline solution C are returned to the recovery unit and jointly undergo recovery treatment with the rinsed alkaline solution A; wherein, the recovery unit includes a precipitation reaction tank and a filter press connected in sequence. Quicklime is added to the precipitation reaction tank for precipitation reaction to obtain the precipitation slurry, and the filter press is used to filter the precipitation slurry to obtain the solid precipitate and the recovered alkaline solution.

[0029] It should be explained in advance that in the process of producing silane by the disproportionation of chlorosilane, both the tail gas discharged from the silane safety valve and the tail gas discharged from the chlorosilane safety valve are tail gases that may be generated to ensure the safe progress of the production process. That is, when the system pressure exceeds the set safety value, the excess pressure is automatically released to prevent the equipment or pipeline from being damaged due to overpressure, and then the tail gas discharged from the safety valve is released. Especially for the tail gas discharged from the chlorosilane safety valve and the chlorosilane tail gas, both of them are by-products or unreacted raw material parts in the process of preparing silane, but the volume of the tail gas discharged from the chlorosilane safety valve is larger, so their treatment methods and the involved conditions are thus different.

[0030] The above treatment method for the tail gas from the disproportionation of chlorosilane to produce silane provided by the present invention effectively removes the harmful substances in the tail gas discharged from the silane safety valve, the silane tail gas, the tail gas discharged from the chlorosilane safety valve, and the chlorosilane tail gas by using sodium hydroxide solution rinsing and quicklime precipitation reaction, and simultaneously realizes the harmless treatment of various tail gases generated in the process of producing silane by the disproportionation of chlorosilane.

[0031] Specifically, in step S2, by passing the tail gas discharged from the silane safety valve and the silane tail gas through a scrubbing system with sodium hydroxide as the scrubbing liquid respectively, harmful substances such as silane in these two types of tail gases can be effectively removed, ensuring the safety and efficiency of subsequent treatment steps, and it is applicable to treating tail gases containing high-concentration silane. In step S3, the tail gas discharged from the chlorosilane safety valve and the chlorosilane tail gas are first subjected to condensation treatment to condense and recover the chlorosilane in them. The first condensed tail gas and the second condensed tail gas separated from the chlorosilane condensate are then mixed and subjected to sodium hydroxide lye scrubbing to remove the remaining chlorosilane therein. The scrubbing tail gas generated during the above scrubbing process is high-purity hydrogen that can be directly vented. In step S4, each scrubbing liquid generated by scrubbing, namely the sodium metasilicate solution, reacts with quicklime to generate insoluble calcium metasilicate and sodium hydroxide. The sodium metasilicate solid can be directly landfilled, and the obtained sodium hydroxide solution is used as the recycled lye to participate in the second scrubbing and the third scrubbing. That is to say, in step S4, through a precipitation reaction, water glass that is difficult to recycle and treat under normal conditions is converted into insoluble substances, avoiding the possible blockage of the corresponding system equipment and pipelines, further removing other harmful substances that cannot be completely removed by scrubbing in the scrubbed lye A, B, and C, and ensuring that the treated filtrate meets the discharge and recycling standards. More importantly, by setting this step, the recycling and reuse of the lye in the entire system are realized, so as to more reasonably utilize the concentrated alkali introduced and used in the first scrubbing process, and ultimately significantly improve the economic and environmental protection performance of the above method, and more efficiently achieve the harmless treatment of various tail gases generated during the production of silane by the disproportionation method of chlorosilane. Further, the mass concentration of sodium hydroxide in the recycled lye is 2% - 5%. Based on the tail gas discharged from the silane safety valve, preferably the first scrubbing liquid is a sodium hydroxide solution with a mass concentration of 10% - 25%, so that the silane in the tail gas discharged from the silane safety valve can react more thoroughly with NaOH in the lye and be removed, which is applicable to treating the tail gas discharged from the silane safety valve containing high-concentration silane, improving the thoroughness and safety of its treatment, and at the same time more efficiently recovering the recycled lye to promote the subsequent treatment process.

[0032] In several typical embodiments, in order to make the scrubbing process in the first scrubbing system, the second scrubbing system, and the third scrubbing system more efficient, and thus more thoroughly remove chlorosilane and silane, achieving a more significant harmless treatment effect, it is preferred that the flow rate of the tail gas discharged from the silane safety valve entering the first scrubbing system is 800 Nm 3 / h - 1200 Nm 3 / h, and more preferably 1000 ± 50 Nm 3 / h; the flow rate of the silane tail gas entering the second scrubbing system is 200 Nm 3 / h - 400 Nm 3 / h, and more preferably 300 ± 50 Nm 3 / h; The spraying amount of the recycled caustic solution entering the second rinsing system is 8 m 3 / h to 12 m 3 / h, more preferably 10 ± 0.5 m 3 / h; The flow rate of the mixed chlorosilane tail gas entering the third rinsing system is 300 Nm 3 / h to 500 Nm 3 / h, more preferably 400 ± 50 Nm 3 / h; The spraying amount of the recycled caustic solution entering the third rinsing system is 20 m 3 / h to 40 m 3 / h, more preferably 30 ± 2 m 3 / h.

[0033] Regarding the rinsing process of the tail gas discharged from the silane safety valve, in order to balance the silane removal effect and the equipment operation cost therein, it is preferred that the first rinsing system includes two sets arranged in parallel. Each set of the first rinsing system includes a rinsing tower and a caustic solution circulation pump configured outside the rinsing tower. The caustic solution circulation pump is used to circulate the sodium hydroxide aqueous solution into the rinsing tower to complete the first rinsing. On this basis, in order to better adapt to different inlet amounts of the tail gas discharged from the silane safety valve, so as to more efficiently achieve its spraying and silane removal effect, it is further preferred that among the two sets of the first rinsing systems, one set is in a continuous operation state and the other set is in standby; meanwhile, the spraying amount of the continuously operating set is less than that of the standby set, and the opening and closing state of the standby set changes with the inlet pressure of the continuously operating set. When the inlet pressure exceeds the threshold value, the standby set changes from the closed state to the open state. The preferred threshold value is 0.075 MPa to 0.15 MPa, more preferably 0.1 ± 0.02 MPa, so as to more efficiently achieve the first rinsing process.

[0034] In addition, in order to achieve a better precipitation effect and improve the harmless treatment efficiency, it is further preferred that the precipitation reaction is carried out under normal temperature and pressure.

[0035] Regarding the components of the above-mentioned tail gas discharged from the chlorosilane safety valve and the chlorosilane tail gas, it is further preferred that the temperatures of the first condensation treatment and the second condensation treatment are each independently -10°C to -40°C, more preferably the temperatures of the first condensation treatment and the second condensation treatment are each independently -20 ± 2°C. By preferably and more preferably the temperatures of the above-mentioned condensation treatment, the chlorosilane components can be more effectively recovered, reducing resource waste. At the same time, a mixed chlorosilane tail gas with a lower chlorosilane content is also obtained, laying a foundation for the subsequent rinsing treatment thereof, and ultimately improving the removal rate of chlorosilane in the entire treatment process flow.

[0036] In several typical embodiments, the recycled lye is divided into a first part, a second part, and a third part, where the first part is used for the second rinsing, and the second part is used for the third rinsing; the method for treating the tail gas from the disproportionation of chlorosilane to produce silane further includes: Step S5, discharging the third part of the recycled lye into a neutralization reaction tank, adding hydrochloric acid to the neutralization reaction tank, and obtaining a sodium chloride solution after the neutralization reaction; the sodium chloride solution is subjected to evaporation crystallization to obtain sodium chloride crystals and condensed water, and the condensed water is returned to Step S4 for pressure filtration treatment to further realize resource reuse. In addition, the excess sodium hydroxide filtrate can also be concentrated and sold directly, thereby further reducing the cost of the above treatment method.

[0037] The above-mentioned various tail gases come from the existing production system of producing silane by the disproportionation of chlorosilane. In several typical embodiments, by weight, the tail gas discharged from the silane safety valve contains 40-45 parts of silane and 50-55 parts of chlorosilane; and / or, by weight, the silane tail gas contains 55-60 parts of silane, 2-4 parts of chlorosilane, and 40-45 parts of nitrogen; and / or, by weight, the tail gas discharged from the chlorosilane safety valve and the chlorosilane tail gas each independently contain 3-5 parts of chlorosilane, 37-40 parts of hydrogen, 55-60 parts of nitrogen, and 1-2 parts of hydrogen chloride.

[0038] The following further describes the present application in detail with specific embodiments, and these embodiments should not be construed as limiting the scope claimed by the present application.

[0039] Unless otherwise defined, all the technical terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0040] It should be noted in advance that the tail gas from the disproportionation of chlorosilane to produce silane processed by the present invention, that is, during the process of producing silane by the disproportionation of chlorosilane, the tail gas discharged from the silane safety valve, the silane tail gas, the tail gas discharged from the chlorosilane safety valve, and the chlorosilane tail gas are obtained. The main component contents are shown in Table 1 below (a small amount of impurity gases are not listed).

[0041] Table 1

[0042] Component and content / % Silane Chlorosilane Hydrogen Nitrogen Hydrogen chloride Tail gas discharged from the silane safety valve 44 55 \ \ \ Silane tail gas 55 2 \ 43 \ Tail gas discharged from the chlorosilane safety valve and chlorosilane tail gas \ 3 37 59 1

[0043] Example 1

[0044] A method for treating the tail gas from the disproportionation of chlorosilane to produce silane, which is carried out using the Figure 1 system shown:

[0045] (1) Feed an aqueous sodium hydroxide solution with a mass concentration of 25% into the first rinsing system as the first rinsing liquid. This system contains 2 spray towers, and each spray is equipped with a separate rinsing system and an alkali liquor circulation pump. Set A is always open but has a small spray volume (10 m 3 / h), while set B has a large spray volume (30 m 3 / h) but is interlocked with the pressure at the inlet of the tail gas discharged from the silane safety valve. Only when the pressure exceeds the set value (0.1 MPa, gauge pressure) will the alkali liquor circulation pump of set B be started. Feed the tail gas discharged from the silane safety valve into the first rinsing system at a flow rate of 1000 Nm 3 / h. After the first rinsing, the rinsed alkali liquor A and the rinsed tail gas A are obtained. The obtained rinsed alkali liquor A is discharged into the precipitation reaction tank, and the rinsed tail gas A can be directly vented;

[0046] (2) Feed the silane tail gas into the second rinsing system of the silane tail gas at a flow rate of 300 Nm 3 / h. The second rinsing liquid used in this rinsing system, that is, the recycled sodium hydroxide alkali liquor with a mass concentration of 5%, is sprayed at a volume of 10 m 3 / h. After the second rinsing, the rinsed alkali liquor B and the rinsed tail gas B are obtained. The obtained rinsed alkali liquor B is also discharged into the precipitation reaction tank, and the rinsed tail gas B can be directly vented;

[0047] (3) The tail gas discharged from the chlorosilane safety valve is subjected to the first condensation treatment at -20°C to obtain the first condensed tail gas and chlorosilane condensate; the chlorosilane tail gas is subjected to the second condensation treatment at -20°C to obtain the second condensed tail gas and chlorosilane condensate. The two chlorosilane condensates are recovered and treated, and the first condensed tail gas and the second condensed tail gas are mixed to obtain the mixed chlorosilane tail gas; then the obtained mixed chlorosilane tail gas is fed into the third rinsing system at a flow rate of 400 Nm 3 / h. The third rinsing system uses an aqueous solution of recycled sodium hydroxide with a mass concentration of 2% as the third rinsing liquid. The mixed chlorosilane tail gas is sprayed at a volume of 30 m 3 / h. After the third rinsing, the rinsed alkali liquor C and the rinsed tail gas C are obtained. The obtained rinsed alkali liquor C is discharged into the precipitation reaction tank, and the rinsed tail gas C can be directly vented;

[0048] (4) The rinsed alkali liquor A, the rinsed alkali liquor B, and the rinsed alkali liquor C have all entered the precipitation reaction tank. Add quicklime (CaO) to the precipitation reaction tank and carry out the precipitation reaction under normal temperature and pressure conditions. The addition amount is 2934 kg until the silicon element in the reaction tank is completely precipitated. During the precipitation process, Na2SiO3 in the three rinsing liquids reacts with CaO and water to form insoluble solid precipitates CaSiO3 and NaOH and obtain a slurry. The slurry is filtered by pressure to obtain the solid precipitate CaSiO3 and the NaOH filtrate.

[0049] (5) The obtained NaOH filtrate is recycled and used as the second eluent and the third eluent to continue to participate in the second elution and the third elution processes. The excess NaOH filtrate is sent to a neutralization reaction tank to react with hydrochloric acid to form NaCl and water. The NaCl aqueous solution is sent to an evaporation crystallization system (multiple-effect evaporation or MVR) to separate out NaCl, and the generated condensed water is preferentially returned to the pressure filtration for flushing and dilution, and the excess condensed water is discharged from the system.

[0050] In the above treatment method, the vented tail gas A after elution, tail gas B after elution, and tail gas C after elution are all hydrogen-nitrogen mixtures, with purities of 100%, 28%, and 60% respectively, and do not contain polluting harmful components. The obtained solid precipitate, namely sodium metasilicate solid, has a purity of 100% and can be directly landfilled, and the sodium hydroxide filtrate solution can be recycled in the above manner.

[0051] That is, the treatment method provided by this embodiment realizes the harmless treatment of the tail gas from the silane disproportionation method for producing silane.

[0052] From the above description, it can be seen that the above embodiments of the present invention realize the efficient harmless treatment of the four kinds of tail gases generated in the process of producing silane by the silane disproportionation method using sodium hydroxide alkali solutions with different concentrations, namely the tail gas discharged from the silane safety valve, the silane tail gas, the tail gas discharged from the chlorosilane safety valve, and the chlorosilane tail gas. Among them, the tail gas after elution generated in the first, second, and third elution systems is high-purity hydrogen and can be directly vented. The sodium metasilicate solution generated by elution reacts with quicklime in a subsequent precipitation reaction tank to form calcium metasilicate and sodium hydroxide, and the sodium metasilicate solid can be directly landfilled, and the sodium hydroxide solution can be recycled.

[0053] It should be noted that the terms "first", "second", etc. in the specification and claims of this application are used to distinguish similar objects and do not have to be used to describe a specific order or sequence. It should be understood that such terms can be interchanged under appropriate circumstances so that the embodiments of the present application described here can be implemented in an order other than those described here.

[0054] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for treating the tail gas of silane produced by the disproportionation of chlorosilane, characterized in that, Including: Step S1: Provide the tail gas from the silane disproportionation process of chlorosilane. The tail gas from the silane disproportionation process of chlorosilane includes tail gas discharged from the silane safety valve, silane tail gas, tail gas discharged from the chlorosilane safety valve, and chlorosilane tail gas; Step S2: The tail gas discharged from the silane safety valve enters the first rinsing system and is first rinsed with an aqueous sodium hydroxide solution with a mass concentration of 10% - 25% to obtain rinsed alkaline solution A and rinsed tail gas A; The rinsed alkaline solution A is sent to the recovery unit for recovery treatment to obtain recovered alkaline solution; The silane tail gas enters the second rinsing system and is second rinsed with the recovered alkaline solution to obtain rinsed alkaline solution B and rinsed tail gas B; Step S3: The tail gas discharged from the chlorosilane safety valve undergoes first condensation treatment to obtain first chlorosilane condensate and first condensed tail gas; The chlorosilane tail gas undergoes second condensation treatment to obtain second chlorosilane condensate and second condensed tail gas; The first condensed tail gas and the second condensed tail gas are mixed to obtain mixed chlorosilane tail gas; The mixed chlorosilane tail gas enters the third rinsing system and is third rinsed with the recovered alkaline solution to obtain rinsed alkaline solution C and rinsed tail gas C; Step S4: Return the rinsed alkaline solution B and the rinsed alkaline solution C to the recovery unit to jointly perform the recovery treatment with the rinsed alkaline solution A; Among them, the recovery unit includes a precipitation reaction tank and a filter press connected in sequence. Quicklime is added to the precipitation reaction tank for precipitation reaction to obtain a precipitation slurry, and the filter press is used to filter the precipitation slurry to obtain a solid precipitate and the recovered alkaline solution.

2. The method for treating the tail gas of silane produced by the disproportionation of chlorosilane according to claim 1, wherein The mass concentration of sodium hydroxide in the recovered alkaline solution is 2% - 5%.

3. The method for treating the tail gas of silane produced by the disproportionation method of chlorosilane according to claim 1, characterized in that, The first rinsing system includes two sets arranged in parallel. Each set of the first rinsing system includes a rinsing tower and an alkaline solution circulation pump configured outside the rinsing tower. The alkaline solution circulation pump is used to circulate the aqueous sodium hydroxide solution into the rinsing tower to complete the first rinsing.

4. The method for treating the tail gas of silane produced by the disproportionation of chlorosilane according to claim 3, characterized in that, Among the two sets of the first rinsing systems, one set is in a continuous operation state, and the other set is in standby; At the same time, the spraying amount of the set in continuous operation is less than that of the standby set, and the opening and closing state of the standby set changes with the intake pressure of the set in continuous operation. When the intake pressure exceeds the threshold, the standby set changes from the closed state to the open state.

5. The method for treating the tail gas of silane prepared by the disproportionation method of chlorosilane according to claim 4, characterized in that, The threshold is 0.075 MPa - 0.15 MPa.

6. The method for treating the tail gas of silane prepared by the disproportionation method of chlorosilane according to claim 5, characterized in that, The threshold is 0.1 ± 0.02 MPa.

7. The method for treating the silane tail gas produced by the disproportionation of chlorosilane according to claim 6, characterized in that, The precipitation reaction is carried out under normal temperature and pressure.

8. The method for treating the silane tail gas produced by the disproportionation of chlorosilane according to any one of claims 1 to 7, characterized in that, The temperature of the first condensation treatment and the second condensation treatment are each independently -10°C to -40°C.

9. The method for treating the tail gas of silane produced by the disproportionation method of chlorosilane according to claim 8, characterized in that, The temperature of the first condensation treatment and the second condensation treatment are each independently -20 ± 2°C.

10. The method for treating the tail gas from the silane disproportionation process of chlorosilane according to any one of claims 1 to 9, characterized in that The recovered alkaline solution is divided into a first part, a second part, and a third part, where the first part is used for the second rinsing, The second part is used for the third rinsing; The method for treating the tail gas from the silane disproportionation process of chlorosilane further includes: Step S5: Drain the recycled lye described in the third part into the neutralization reaction tank, and add hydrochloric acid to the neutralization reaction tank. After neutralization reaction, a sodium chloride solution is obtained; The sodium chloride solution is subjected to evaporation crystallization to obtain sodium chloride crystals and condensed water, and the condensed water is returned to Step S4 for the pressure filtration treatment.

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